This application proposes to investigate cellular immunity in narcotic addiction. This will be done by determining relative and absolute numers of B- and T-lymphocyte subpopulations and the ability of these cells to be stimulated by mitogens. The effect of various opiate derivatives on the mitogenic stimulation will also be determined. These studies will be performed in human addicts before and during methadone treatment. They will be performed also in mice and rats at various stages of administration of opiates to produce addiction and under withdrawals and methadone treatment conditions. The experiments in animals are necessary because of the lack of adequate controls for the human addicts and to establish whether addiction per se is a factor contributing to the increased susceptibility to infections in this population in which the risk of exposure to infective agents due to unsanitary injection conditions is particularly high.